Solar reflectors are intended for equipping solar power plants, which, in a known manner, usually comprise a large number of mirrors, arrayed along the arcs of concentric circles, in order to reflect solar radiation to a boiler positioned at the top of a tower and located in the center of the array of mirrors. The boiler feeds steam to a turbine located at the base of the tower which in turn drives an electrical generator. Naturally it is necessary periodically to change the orientation of each of the mirrors in order for the reflected solar light to continue to be projected onto the boiler and, with a view to achieving this, the mirrors are mounted on adjustable bases, the position of which is automatically adjusted at regular intervals.
In order to prevent the luminous spot formed by each mirror on the receiver of the boiler from spreading beyond the limits of the receiver, the mirrors must be close in shape to a large radius spherical mirror.
Such reflectors must fulfill a certain number of requisites, among which are the following:
(a) they must be relatively inexpensive, in order for the solar power station to be competitive with traditional electrical generating plants;
(b) they must be reliable, so as to curtail replacement, maintenance and adjustment costs;
(c) they must keep a shape close to that of the ideal convergent mirror, in spite of deformation due to wind, heat and their own weight; and
(d) they must be relatively lightweight, in order to simplify the design of the swivel base.
With a view to meeting these conditions, it has already been proposed, by the Saint-Gobain Techniques Nouvelles corporation, in French patent application Ser. No. FR 76 07756 and published under No. FR 2 344 852, to build convergent reflectors comprising a frame which supports a plurality of reflecting elements or panels, at least one of which is appreciably cylindrical and results from the deformation of a rectangular flat strip. Each of the panels are carried on the frame by means of elastomer edge strips which engage the long sides of the panels and also engage flanges formed integrally with the frame.
In constructing these reflectors, the rectangular reflecting strips are deformed at the work site by means of bending stresses applied along the entire length of the long sides of the strips when they are put into place on the supporting frame, while the short sides are left free during the bending of the long sides. More specifically, elastic deformation is imparted at the work site to a sectional member by the use of a template where the sectional member is destined to support the edge strip of a reflector panel and the sectional member thus deformed is fastened to the reflector frame.
In ordinary practice, reflectors of this type made in this manner comprise part of a rigid structure which can be directed in different directions with respect to a base anchored to the ground and where the rigid structure has a flat framework which supports T irons, arranged for example in vertical or horizontal lines, forming cambered members which are brought onto the reference sphere by shaping. A shaping machine rolling on curved rails and equipped with a template arranged in a vertical plane makes it possible to place and fix each sectional member on a beam in the desired position, after it has been cambered to the desired curvature.
This method makes it possible to rapidly assemble each mirror, but it requires a heavy, costly forming structure. This method also has the drawback that it can be utilized only at the site where the mirror is to be installed.
It is therefore an object of my invention to provide mirrors of the same general type as discussed above and which lend themselves to rapid assembly but which are more economically assembled in view of the fact that they do not require the use of a machine for forming the structural members one by one opposite each mirror at the work site.
It is an object of the invention to provide for a swiveling solar reflector the reflecting panels of which are supported by prefabricated cambered members which are assembled at the erection site of the reflector before installing the reflecting panels, after which the necessary adjustments are made to bring the panels into proper positioning.